In one method of manufacturing electrical terminals, the terminals are stamped and formed from metal strip and are attached to a carrier strip. This carrier strip is useful for strip feeding the terminals through successive manufacturing operations. One necessary manufacturing operation involves plating, i.e., electroplating the electrical contact surfaces of the strip fed terminals with a contact metal, usually noble metals or noble metal alloys. These metals are characterized by good electrical conductivity and little or no formation of oxides that reduce the conductivity. Therefore, these metals, when applied as plating, will enhance conductivity of the terminals. The high cost of these metals has necessitated precision deposition on the contact surfaces of the terminals, and not on surfaces of the terminals in which plating is unnecessary.
Apparatus for plating is called a plating cell and includes an electrical anode, an electrical cathode comprised of the strip fed terminals, and a plating solution, i.e., an electrolyte of metal ions. A strip feeding means feeds the strip to a strip guide. The strip guide guides the terminals through a plating zone while the terminals are being plated. The plating solution is fluidic and is placed in contact with the anode and the terminals. The apparatus operates by passing electrical current from the anode through the plating solution to the terminals. The metal ions deposit as metal plating on those terminal surfaces in contact with the plating solution.
There are disclosed in U.S. Pat. Nos. 4,384,926, 4,427,498 and 4,555,321, owned by this Assignee, plating apparatii in which the interior surfaces of strip fed terminals can be plated by supplying plating fluid through nozzles and over associated anode extensions that are mounted for reciprocation into and out of the interiors of terminals. In the first two patents, the anode extensions are mounted within their associated nozzles. In the third patent, the anode extensions are mounted separately and apart from the nozzles and enter the terminals from a different direction than that of the plating fluid.
The apparatii disclosed in the three referenced patents are designed to be used with stamped and formed terminals, wherein the contact zone is located inside the formed terminal. To selectively plate the contact zone the anode extension must be moved inside the terminal and preferably to the center of the formed terminal. The distance traveled by the anode extension, therefore, is greater than the thickness of the stock material.
The above apparatii, however, present problems when used to plate strips of essentially flat terminals whose contact zones are located on surfaces that are perpendicular to the length of a strip, such as between the tines of a forked terminal. The depth of the contact zone for such a terminal is essentially equal to the thickness of the stock material. The center of the contact zone, therefore, would be half of the thickness of the material. Moving the anode extensions through such a short travel distance has been found to be unsatisfactory owing to dimensional and tolerance requirements.
It is an object of the present invention to provide an apparatus for selectively plating strips of stamped terminals.
It is a further object of the present invention to provide an apparatus wherein essentially only the contact zone of each terminal in a strip of terminals is plated.
It is an additional object of the present invention to provide an anode extension in the contact zone of each terminal as the terminals are plated.
Additionally, it is an object of the invention to provide a means for positioning the anode extension in the contact zone.
It is also an object of the invention to provide an apparatus that can be readily adapted to terminals having different center line spacings.
It is another object of the invention to provide a process for plating interior surfaces of flat terminals.